AMD and Atrophy of the Visual Cortex
Investigative Ophthalmology and Visual Sciences
Hanson et al. set out to observe both short- and long-term changes in the visual cortex in patients with wet age-related macular degeneration (AMD). They found atrophic and retinotopic changes in these patients.
For this prospective study, the researchers recruited 10 participants who had established bilateral dry AMD and new-onset unilateral wet AMD. The patients were treated with anti-VEGF injections and screened with magnetic resonance imaging (MRI) at baseline and at a mean of 3.5 months (range, 3-4 months) after baseline. Seven of the 10 patients also underwent MRI a mean of 4.8 years (range, 3.8-6.1 years) after baseline.
Best-corrected visual acuity (BCVA) and central retinal thickness (CRT) measurements were collected at all time points. Main outcome measures included changes in cortical anatomy assessed in the occipital lobe as a whole and in the specific projection zones associated with either the intact or lesioned retinal areas.
Results were as follows: No significant changes in cortical volume were observed at the short-term assessment. However, reduction in cortical volume was evident at the long-term evaluation. In the intact projection zone, minimal changes were observed in cortical thickness at both follow-up evaluations. However, the lesion projection zone was significantly thinner at the long-term assessment than at the short-term evaluation.
BCVA improved over both short- and long-term time frames in treated eyes, although this improvement was not significant. A long-term decrease in BCVA in the untreated eye was noted in five of the seven patients who completed that assessment. With regard to CRT, a significant decrease was noted at the short-term follow-up; this remained significant at the long-term assessment.
The researchers concluded that longstanding unilateral loss of input to the visual cortex results in significant atrophy—and that there is a window, at least within the first few months after diagnosis, in which no atrophy is evident. This suggests that detrimental changes in the visual cortex emerge relatively slowly, they said, and they noted that future longitudinal studies would benefit from assessing the visual cortex between three and 12 months after diagnosis. This study also demonstrates that transsynaptic retrograde degeneration, previously described in vascular or compressive disorders of the optic pathways, also may occur when focal retinal disease is present.
The original article can be found here.